Surge in Passive House construction driven by real savings in energy costs

Photo / Tim Greenway

Rand Ardell, director of marketing and communications at Waynflete and Millard Nadeau, a Wright-Ryan Construction superintendent, at Waynflete, where Passive House construction is being used on the lower school addition.

Chris Corson of Ecocor says a decade ago he had to educate clients about Passive House concepts. Today, the company has had to double its space to keep up with demand.

Passive House principles

Certified Passive House structures (the term Passive House applies to commercial buildings as well), have strict space heating and cooling limits, as well as airflow and temperature limits. (see passivehouse.org for details). To achieve the requirements, all certified Passive House structures must include:

Thermal insulation: All opaque building components of the exterior envelope of the house must be well-insulated.

Passive House windows: The window frames must be well-insulated and fitted with glass filled with argon or krypton to prevent heat transfer.

Ventilation heat recovery: Efficient heat recovery ventilation is key, allowing for a good indoor air quality and saving energy. In Passive House, at least 75% of the heat from the exhaust air is transferred to the fresh air again by means of a heat exchanger.

Airtight building: Uncontrolled leakage through gaps must be smaller than 0.6 of the total house volume per hour during a pressure test at 50 Pascal (both pressurised and unpressurised).

Absence of thermal bridges: All edges, corners, connections and penetrations must be planned and executed with great care, so that thermal bridges can be avoided. Thermal bridges which cannot be avoided must be minimised as far as possible.

Cornerspring Montessori School in Belfast could pass for any modern school; so could the Friends School of Portland in Cumberland.

In Portland, the ultra-modern lower school addition at Waynflete complements a converted barn, built in 1840.

Across the city, 45-apartment Bayside Anchor stands out mostly because it's bright green in a sea of gray and brick.

In Brewer, the Village Centre apartment complex doesn't look much different from other new apartment buildings.

But the recent developments, all built to Passive House standards, are very different on the inside from their neighbors.

"A Passive House can look like any house," says Chris Corson, founder and technical director of Ecocor, which builds Passive House single-family homes. The difference is in how it's built.

"It has thicker walls, thicker windows, more insulation," he says, and adheres to the other principles that make a building so energy efficient that it can be heated or cooled largely by environmental means.

A high-performance building 'envelope'

The concept of the "passive house" goes back centuries — people figuring out how to be comfortable in their home no matter what it's like outside.

The modern concept evolved out of decades of research into "super-insulated" buildings and energy efficiency. The Passivhaus Institute was founded in the late 1980s in Germany by physicist Wolfgang Feist and scientist Bo Adamson.

Certified Passive House construction has five requirements: thick insulation, airtight construction, thick and well-placed windows, prevention of moisture migration and a steady supply of fresh air.

While Passive House is often confused with LEED, there's a difference. LEED, or Leadership in Environmental and Energy Design, is about overall environmental impact. Passive House is about energy efficiency.

"This isn't LEED, this isn't Energy Star," Corson says. "It's about high-performance building envelopes that are designed to meet the international Passive House standards."

Focus on energy use

At Waynflete School, a 33,000-square-foot addition is expected to be ready in September.

"At the beginning of the design process, we looked at LEED versus Passive House," says Cordelia Pitman, director of preconstruction services for Portland-based construction manager Wright-Ryan Construction. At the time, Wright-Ryan had just finished the Passive House Village Centre in Brewer.

The decision wasn't difficult. "It focuses more on energy use, not where did your trusses come from," she says.

The private school of about 550 students agreed energy savings meant more money could go into education.

Besides the Brewer and Waynflete projects, Wright-Ryan managed construction on the 45-unit Bay Anchor, which was completed last year.

Warren Construction Group, based in Freeport, is another firm building to Passive House standards, including the $2.3 million Friends School and the $6.3 million high school addition at Maine Coast Waldorf School in Freeport.

At Waynflete, director of marketing and communications Rand Ardell and project superintendent Millard Nadeau, of Wright-Ryan, point out the features of the planned addition, including differences between Passive House and standard construction.

The wall insulation panels are more than eight inches thick and spray foam provides a vapor barrier at connection points. The roof insulation is 16 inches, nearly triple the standard of six inches. Equipment in the ceiling provides ventilation while keeping the temperature moderate. Triple-pane windows are placed for maximum sun exposure. The building will be heated by heat pumps.

"It's more efficient, you're not using oil or burning natural gas," Nadeau says.

The addition was angled to capture the sun.

Recent surge

Maine's Passive House pioneer was Unity College, where in 2011 G-O Logic of Belfast built a 2,100-square-foot residence that houses 10 students, Terrahaus.

The 15,500-square-foot Friends School was built in 2015.

Since then, there has been a surge of Passive House commercial projects, including 48-unit Village Centre in 2016; the Maine Coast Waldorf School high school addition in 2017; 45-unit Bayside Anchor in 2017; and Cornerspring Montessori School in 2017.

As of 2016 there was 1.1 million square feet of certified Passive House construction in the U.S, according to the Passive House Institute.

There have been far more residential projects than commercial ones in Maine, Corson says.

His company, Ecocor, built its first Passive House in 2012, shortly after G-O Logic built the first one in the state.

Corson's company has built 60 homes, not all in Maine, since then. Ecocor fabricates much of the building in its Searsmont plant, but the homes are custom-designed.

In nearby Belfast, G-O Logic last year launched a prefabricated line with a choice of designs.

While residential building is where most of the Passive House effort is, Corson says the commercial surge is what will drive the industry.

"For there to be wide-scale adoption [of Passive House building] you need the commercial projects," Corson adds.

'What are you investing in?'

Corson, who has been in the construction and design industry for decades, didn't think Passive House construction would catch on when he first started building that way a decade ago.

"I didn't think there was ever going to be a market for us," he says.

He was trained in engineering and technology and remains fascinated by them. He has always been environmentally conscious. When the stock market crashed in 2008, he was ready for a change.

He started a design and construction firm that only built to Passive House standards. At first, there was a learning curve for clients.

"It took a great degree of conversation and teaching clients," he says.

But a lot of his first clients had engineering or science backgrounds. "They got it from the beginning," he says.

The concept is simple, he says. It may cost 10% more to build the super-tight, highly insulated house, but the long-term energy savings and lack of environmental impact pay off.

"The conversation with homeowners is, 'What are you investing in? Fit and finish and frills? Or components that are going to last the longest — windows, roofs" and energy savings, Corson says.

These days it's not the homeowners who need convincing, though, but appraisers and banks, which don't always see the added value of a Passive House, he says.

When Ecocor began building certified Passive House components in 2013, it was the first manufacturer in the nation to do so, Corson says. Five years later, business is good enough that the company is moving out of its leased 14,000 square feet nestled behind Searsmont's town center into 20,000 square feet in neighboring Belmont.

Corson says, aside from business increasing, the company, which employs about 20, needs more office space.

A lot of the work is done on computers. The design evolves with thousands of components into a 3D model before the parts are built.

While the design takes about six months, the parts are fabricated in about 30 days, and builders are on site for seven to 10 days.

Checking the boxes

Corson says building homes isn't going to get less expensive, and while Passive House construction is considered by many "boutique," it will move toward the norm.

"Regardless of political persuasion, I think Passive House checks all the boxes," he says. "Even if one were to assert global warming doesn't exist … it still checks off fiscal responsibility, health, air quality."

At Waynflete — where everyone from the builders and designers to school officials and students are excited enough about the construction that Ardell and Nadeau do a monthly progress video — that future is here.

"In general it's gaining a lot of momentum in the U.S." says Mark Bourgeois of Wright-Ryan. He says the availability of the products and understanding of the building practices is helping.

While the $12 million project (which includes the renovation to the older building) is initially more expensive than standard construction, Ardell says, the long-term benefits exceed the cost.

Aside from the Passive House savings, the project checks off other important boxes for the school.

"Our principles are take care of yourself, take care of others and take care of the environment," Ardell says. "This building is doing that."